1. Field of the Invention
The present invention relates to an aminodibenzofluorene derivative, a material for an organic electroluminescence (EL) device obtained by using the same, a light emitting material for an organic EL device, an organic EL device, an equipment comprising the same and a light emitting organic solution, specifically to an organic EL device which has a long lifetime and a high current efficiency and which provides blue light emission, an aminodibenzofluorene derivative materializing the same, a material for an organic EL device obtained by using the same, a light emitting material for an organic EL device, an organic EL device, an equipment comprising the same and a light emitting organic solution.
2. Related Art
An organic electroluminescence device (hereinafter “electroluminescence” shall be abbreviated as EL) is a spontaneous luminescent device making use of the principle that a fluorescent substance emits light by recombination energy of holes injected from an anode and electrons injected from a cathode by applying an electric field. Since an organic EL device of a laminate type driven at a low voltage was reported by C. W. Tang et al. of Eastman Kodak Company (C. W. Tang and S. A. Vanslyke, Applied Physics Letters, Vol. 51, p. 913, 1987 and the like), researches on organic EL devices comprising organic materials as structural materials have actively been carried out. Tang et al. use tris(8-quinolinolate)aluminum for the light emitting layer and a triphenyldiamine derivative for the hole transporting layer. The advantages of the laminate structure include an elevation in an efficiency of injecting holes into a light emitting layer, a rise in a production efficiency of excitons produced by blocking electrons injected from a cathode to recombine them and shutting up of excitons produced in a light emitting layer. As shown in the above example, a two-layer type comprising a hole transporting (injecting) layer and an electron transporting and light emitting layer and a three-layer type comprising a hole transporting (injecting) layer, a light emitting layer and an electron transporting (injecting) layer are well known as the device structures of an organic EL device. In the above laminate type structural devices, device structures and forming methods are studied in order to enhance a recombination efficiency of holes and electrons injected.
Known as light emitting materials are light emitting materials such as chelate complexes such as a tris(8-quinolinolate)aluminum complex, coumarin derivatives, tetraphenylbutadiene derivatives, bisstyrylarylene derivatives, oxadiazole derivatives and the like. It is reported that light emission of a blue color to a red color in a visible region is obtained from them, and it is expected that a color display device is materialized (for example, a patent document 1, a patent document 2, a patent document 3 and the like).
Devices prepared by using bisanthracene derivatives as a light emitting material are disclosed in a patent document 4 and a patent document 5. Bisanthracene is used as a blue light emitting material, but an efficiency and a lifetime thereof do not reach practicable levels and are unsatisfactory.
Also, devices prepared by using symmetric pyrene derivatives as a light emitting material are disclosed in a patent document 6, a patent document 7, a patent document 8 and a patent document 9. The above symmetric pyrene derivatives are used as a blue light emitting material, but a lifetime of the devices has been required to be improved.
Further, a device using a dibenzofluorene derivative as a light emitting material is disclosed in a patent document 10, but the specific physical property values are not described. Also, a high molecular organic EL device prepared by using a benzofluorene derivative is disclosed in a patent document 11. The above (di)benzofluorene derivatives are used as a blue light emitting material, but a color purity and a lifetime of the devices have been required to be improved.
Patent document 1: Japanese Patent Application Laid-Open No. 239655/1996
Patent document 2: Japanese Patent Application Laid-Open No. 138561/1995
Patent document 3: Japanese Patent Application Laid-Open No. 200289/1991
Patent document 4: Japanese Patent No. 3008897
Patent document 5: Japanese Patent Application Laid-Open No. 12600/1996
Patent document 6: Japanese Patent Application Laid-Open No. 118682/2001
Patent document 7: Japanese Patent Application Laid-Open No. 63988/2002
Patent document 8: Japanese Patent Application Laid-Open No. 75567/2004
Patent document 9: Japanese Patent Application Laid-Open No. 83481/2004
Patent document 10: International Publication No. 03/051092
Patent document 11: International Publication No. 04/061047